Construction Stage and Seismic Analyses of Cable-stayed Bridges

Abstract

The first part of this dissertation presents a study on effect of different parameters on behaviour a cable-stayed bridge, whereas the second part deals with seismic analysis of an extra-dosed bridge (hybrid girder-cable stayed bridge) proposed to be constructed in Delhi. The construction procedure and general design details of the cable stayed bridges are discussed. Forward construction stage analysis is performed on the analytical model. In this study the seismic response of the extra-dosed bridge is examined using different analysis procedures viz. response spectrum analysis, linear time history analysis using uniform ground excitation and multi-support excitation. The analysis results of beam forces, cable forces, displacements are compared. Further, the significance of geometric nonlinearity due to cable sag is examined by conducting large displacement analysis. The cable is modelled using equivalent truss elements in the linear analysis which accounts for cable sag effect implicitly, whereas in large displacement analysis, the cable is modelled as catenary element. The difference in beam forces and cable forces are compared. The study shows that multi-support excitation is very important in the case of dynamic analysis as the response spectrum analysis and time history analysis using uniform ground excitation under-estimates the force demands in the structure especially the axial force demand in the girder elements. It is also observed that the cable sag effects may be considered using equivalent truss method and the use of elastic catenary element is not necessary for extradosed bridges.